Thread safety refers to the property of a program or data structure that ensures safe execution by multiple threads at the same time. When multiple threads access shared resources, such as variables or objects, without proper management, it can lead to unpredictable behavior or data corruption. To achieve thread safety, developers often use techniques like locks, semaphores, or other synchronization mechanisms to control access to shared resources. In programming languages like Java or C++, thread safety is crucial for building reliable applications, especially in environments where tasks run concurrently. By ensuring that only one thread can modify a resource at a time, developers can prevent issues like race conditions, where the outcome depends on the unpredictable timing of thread execution.